Selective alkyl ether cleavage by cationic bis(phosphine)iridium complexes.

Catalysts capable of heterolytic silane activation have been successfully applied to the conversion of alkyl ethers to silyl ethers via C-O bond cleavage. The previously-reported cationic pincer-supported iridium complex for this transformation suffers from poor selectivity with regard to monodealkylation of substrate ethers. We demonstrate that a simple non-pincer iridium complex offers improved selectivity and is capable of benzylic ether cleavage in the presence of reductively-labile alkyl and aryl halide functionality. Preliminary mechanistic experiments suggest a neutral tetrahydridosilyliridium resting state which is consistent with previous mechanistic hypotheses. These experiments suggest that a pincer ligand framework is not required for activity in ether cleavage reactions and that simple cationic bis(phosphine)iridium complexes may offer improved selectivity profiles for applications to more-complex substrate molecules.

Computer-Aided Design and Biological Evaluation of Diazaspirocyclic D4R Antagonists.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra, resulting in motor dysfunction. Current treatments are primarily centered around enhancing dopamine signaling or providing dopamine replacement therapy and face limitations such as reduced efficacy over time and adverse side effects. To address these challenges, we identified selective dopamine receptor subtype 4 (D4R) antagonists not previously reported as potential adjuvants for PD management. In this study, a library screening and artificial neural network quantitative structure-activity relationship (QSAR) modeling with experimentally driven library design resulted in a class of spirocyclic compounds to identify candidate D4R antagonists. However, developing selective D4R antagonists suitable for clinical translation remains a challenge.

Selective demethylation of O-aryl glycosides by iridium-catalyzed hydrosilylation.

The cleavage of alkyl ethers by hydrosilylation is a powerful synthetic tool for the generation of silyl ethers. Previous attempts to apply this transformation to carbohydrate derivatives have been constrained by poor selectivity and preferential reduction of the anomeric position. O-Aryl glycosides are found to be stable under iridium- and borane-catalyzed hydrosilylation conditions, allowing for alkyl ether cleavage without loss of anomeric functionality. A cationic bis(phosphine)iridium complex catalyzes the selective 3-demethylation of a variety of 2,3,4-tri-O-methyl pyranoses, offering a unique approach to 3-hydroxy or 3-acetyl 2,4-di-O-methylpyranoses.